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Old 04-03-2013, 03:32 AM   #1
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Default Normal AFR fluctuations at WOT

So with my Miata and other cars I've ridden in each car has a variance in the AFR at WOT from the target, most have been +/- .2 or +/-.3 in the well tuned cars. However, I was curious if there was a standard for this. I searched online a lot for the answer and I couldn't find anything that specifically answered this question. For example my WOT target AFR is 12.8, as I run batch injection on my 1.6 wired ECU I see a variance of +/- .3 AFR as I sweep through the rpms. This translates to seeing AFR's from 12.5-13.1. Is this normal behavior or poor tuning? What is the ideal variance of your AFR with a good tune?
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Old 04-03-2013, 05:05 AM   #2
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I'm sure the batch injection isnt helping make this any better. The stock ecu kept the afrs within .1 of 14.7 at cruise. Rather impressive. Dont remember for wot.
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Old 04-03-2013, 08:45 AM   #3
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Maybe the changes from NA97 to NB were pretty significant, but my 97 stock ECU certainly did/does not keep AFRs within +/- 0.1 of 14.7 at cruise. Since it uses a narrowband input to determine fueling, I would see oscillations/sweeps from approximately 14.2 to 15.2 on the wideband.
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Old 04-03-2013, 01:39 PM   #4
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Quote:
Originally Posted by triple88a View Post
I'm sure the batch injection isnt helping make this any better. The stock ecu kept the afrs within .1 of 14.7 at cruise. Rather impressive. Dont remember for wot.
That is very impressive, and for cruise I could image this being possible since it is a steady state event like idle.

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Originally Posted by jnshk View Post
Maybe the changes from NA97 to NB were pretty significant, but my 97 stock ECU certainly did/does not keep AFRs within +/- 0.1 of 14.7 at cruise. Since it uses a narrowband input to determine fueling, I would see oscillations/sweeps from approximately 14.2 to 15.2 on the wideband.
That sounds about right for something running a narrowband, I'm able to get mine a bit more stable but I still see oscillation at cruise.
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Old 04-04-2013, 02:50 PM   #5
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Here is my data log from my 135WHP run on the dyno and MSQ from the run for example. When running VE Analyze after the run it wanted zero changes to the MSQ so I assume the variance in this case is at an ideal amount. You'll see the +/- .3 as it sweeps through the RPMs.
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